In a wireless communication networks, there are communication nodes, for example base stations. The base stations normally comprise sector-covering antenna arrangements. Such an antenna arrangement comprises a number of antenna ports corresponding to branches for uplink and downlink, where downlink denotes transmission, TX, from the base station to other nodes such as mobile terminals, and uplink denotes reception, RX, to the base station from other nodes such as mobile terminals. A downlink branch is thus a TX branch and an uplink branch is thus an RX branch.
Normally a typical system configuration may comprise two TX branches in the form of transmission channels and two RX branches in the form of reception channels, but system configurations with two TX branches and four RX branches are more attractive since the additional two RX branches provide large uplink improvements for a relatively small cost and volume increase. However, two additional antenna ports are required in the antenna arrangement.
An even more complex antenna arrangement is required when two TX and four RX branches on a frequency band shall be combined with two TX and four RX branches from another frequency band.
The most common configuration existing today for such a dual-band antenna arrangement, with two TX branches and four RX branches, is a dual-column antenna with individual tilt for all antenna ports and frequencies. This can be accomplished by placing diplexers after the antenna elements and having individual phase shifters for each frequency band and polarization.
Existing solutions for such a dual-band antenna arrangement, with two TX branches and four RX branches, based on compact dual column antennas, thus require one diplexer per antenna subarray and polarization. For example, a standard antenna may feature 4-9 subarrays and two polarizations per antenna column. This means that dual column antenna contains 16-36 diplexers and 8 phase shifters. It is a problem to be able to fit all these components without adding a significant volume increase of the antenna, especially for bands with a small frequency separation.
There is thus a need for a less complicated dual-band antenna arrangement in a node, where the antenna arrangement in its least complicated form has two transmission channels and four reception channels. In a typical case, the antenna arrangement has four transmission channels and eight reception channels.